Typical offset lithographic printing presses comprise five basic components: a web feed, a printing unit or units, a dryer, a chill roll unit and a folder. The printing press has one or more printing units depending upon the number of colors which are needed for the particular printing task. A printing unit is needed for each color. A typical newspaper press only has one printing unit for the color black. A full color printing press may have either four or five printing units depending upon whether or not a special color is used. The three primary printing colors are yellow, cyan and magenta.
The web feed feeds a web, i.e., one continuous sheet, of paper through the priming units. A web is usually between 38.0 inches and 54.0 inches wide. Typically, up to six pages may be printed across the width of the web. After the web exists the printing unit(s), it passes through a dryer. Water is used in applying the ink to the paper. Consequently, the paper is wet exiting the printing units. The dryer is used to dry the ink onto the paper so that it does not smear.
After the web exists the dryer, it passes through the chill roll unit which comprises a plurality of chill rollers which cool down the web before it passes through the folding section of the printing press. The folding section of the printing press, or folder as it is also known, is a separate stand-alone unit which connects to the end of the chill roll unit which in turn connects to the end of the dryer. The dryer in turn connects to the priming units. The folder folds and cuts the web of paper into signatures, which are booklets containing a plurality of pages for subsequent insertion into other signatures as in a newspaper or binding as in a magazine or book.
Before the web is cut laterally, it is folded longitudinally by a device known as a former board, which is a triangular board over which the web is draped. A pair of forming rollers are also provided which cooperate with the former board to form the primary longitudinal fold. Prior to being folded lengthwise, the web may also be cut across its width into a plurality of strips known as ribbons. Once folded lengthwise, each ribbon passes through an associated pair of cutting cylinders which cuts the ribbon laterally. One of the pair of cylinders has at least one knife, and the other has an at least one associated anvil, which cooperates with the knife to form the cut in the associated ribbon.
In known devices, two layers of VELCRO.TM. brand gripping material are placed on the outer circumferential surfaces of the cutting cylinders. The VELCRO.TM. brand gripping material surfaces are provided for corrugating the folded ribbons and imparting a certain stiffness to the ribbons so that they exit the cutting cylinders in a straight configuration. This facilitates the transfer of the ribbons into the high speed section of the folder.
Each layer of VELCRO.TM. brand gripping material is typically formed by placing a plurality of 0.75 inch wide velcro strips spaced 1.50 inches apart around virtually the entire circumference of the cylinders. Approximately 50 strips of VELCRO.TM. brand gripping material are used in each layer. The VELCRO.TM. brand gripping material is attached to the cylinder with an adhesive. The longitudinally folded web passes through the cutting cylinders at a high speed, up to 3,000 feet per minute. Over time, the friction between the web and the VELCRO.TM. brand gripping material surface of the cutting cylinders causes the VELCRO.TM. brand gripping material to wear out. In fact, one or more VELCRO.TM. brand gripping material strips must be replaced on a somewhat regular basis.
Replacing the VELCRO.TM. brand gripping material strips is a time consuming task. It requires peeling off the worn VELCRO.TM. brand gripping material strips, scraping residue adhesive, cleaning the cylinder with solvents, properly aligning the new VELCRO.TM. brand gripping material strips on the cylinder and then mounting them to the surface of the cylinders. This can take anywhere between one-half an hour to three hours depending on the amount of VELCRO.TM. brand gripping material strips that needs to be replaced. Also, additional time is required to allow the strips to cure. Because the folder is in-line with the printing units, when the folder is shut down for servicing, the entire printing press must be shut down. Accordingly, the time spent in replacing the VELCRO.TM. brand gripping material strips is lost printing time. Such "down time" can be very costly for the printer.
The present invention is directed to overcoming or at least minimizing some of the problems mentioned above.